Conventionally, there is known the technology for converting geographical information such as an address or a place name into coordinate information about a latitude and longitude (for example, see Patent Documents 1 and 2). The technology is referred to as geocoding and is widely used practically in an application using a map. For example, there is provided a system obtained by combining the geocoding and the geographical visualizing technology referred to as GIS (Geographic Information System). According to the system of this type, for example, values linked to addresses in a database, totalization results thereof or the like can be displayed to be easily understood visually in a corresponding position on a map based on a latitude and longitude converted from the address.
Referring to the information processing device described in the Patent Document 1, address book information and latitude and longitude information acquired based on the address information are stored as a conversion table corresponding to each other, and a latitude and longitude of the position is obtained from a prefecture, a city, a town and a street of the address information by utilizing the conversion table. Map image information is retrieved based on the latitude and longitude information and is synthesized with the address book information, and an address book or a current position is displayed.
The information processing device described in the Patent Document 1 stores, in the conversion table, latitude and longitude information about a spot corresponding to an address according to a hierarchical structure of “prefecture•city•town•street”. Even if an address to be input is not complete like “1-chome, Yoshidacho, Totsuka-ku, Yokohama-shi, Kanagawa-ken” but only a high order hierarchy such as “Yokohama-shi, Kanagawa-ken” or “Totuka-ku, Yokohama-shi, Kanagawa-ken”, it is possible to obtain coordinates of spots corresponding to respective addresses.
Referring to the coordinate imparting system described in the Patent Document 2, moreover, a latitude and longitude database causing an address and position coordinates to correspond to each other is prepared and the position coordinates corresponding to the input address are retrieved from the database. In the retrieval, by narrowing position coordinates every hierarchy based on an administrative district, it is possible to perform the retrieval while compensating for the imperfection of the input address information every hierarchy. Consequently, it is possible to enhance retrieval accuracy.
Patent Document 1: Japanese Laid-Open Patent Publication No. 1996-50594
Patent Document 2: Japanese Laid-Open Patent Publication No. 2003-223453